In the past, in-cab signaling systems have operated on the principle of coded pulses transmitted between signal locations and a locomotive via the physical rails of the track or from loops buried beneath the tracks. The actual pulse is determined by the aspect (color) of the signal being approached by a given train. The coded pulses are received from the rails or loops by equipment on-board the locomotive, and the aspect of the signal that the train is approaching is displayed to the locomotive engineer.
Additionally, some on-board in-cab signal equipment have provided automatic train stop (ATS). ATS typically requires the locomotive engineer to acknowledge when the train receives a more restrictive signal aspect and to take appropriate action to comply with that signal aspect. If the locomotive engineer fails to take appropriate action, the on-board equipment will bring the train to a complete stop prior to violating the signal aspect.
While these systems have been utilized in the past, they do have several significant problems associated with them.
First of all, typically there is a relatively high cost associated with the track side and on-board equipment of both of these prior art systems. Secondly, in the track transmission line system the varying resistance of and between the rails (ballast resistance) can prevent the coded pulses from traveling the required distance from the signal to the locomotive. It can also be distorted to the point where the on-board equipment can not properly decode it, thus possibly creating an unsafe condition. Thirdly, the track based transmitters and the on-board in-cab signal receivers can drift in frequency causing the pulses to be undetectable. Lastly, in the buried loop system the time for communicating between the locomotive and the signal is limited by the size and number of loops and the time the locomotive is located over the loops, thus creating an "intermittent" type in-cab signaling system as opposed to a "continuous" system as proposed by this invention. The systems typically found in the prior art only provide information to the approaching locomotive. They do not typically provide a means for the transfer of information from the locomotive to other railroad entities. The present invention overcomes that problem. When the RF connection is made with specific signal locations that are uniquely equipped to accept information from an approaching locomotive, that locomotive can transmit data such as its electrical and mechanical health status, consumable levels and other pertinent operating data.
Consequently, there exists a need for improvement in in-cab signaling systems which do not exhibit all of the shortcomings of the prior art.